The present disclosure relates to subject matter contained in Japanese patent application No. 3-255287 (filed on Oct. 2, 1991), Japanese patent application No. 3-256279 (filed on Oct. 3, 1991), Japanese patent application No. 3-256280 (filed on Oct. 3, 1991), Japanese patent application No. 3-271613 (filed on Oct. 21, 1991), Japanese patent application No. 4-228112 (filed on Aug. 27, 1992) and Japanese patent application No. 4-228113 (filed on Aug. 27, 1992), which are expressly incorporated herein by reference in their entireties.
1. Field of the Invention
The present invention relates to an endoscope having a solid-state image pickup device which is disposed in the distal end portion of an insert part thereof.
2. Description of the Prior Art
In general, a signal cable that is connected to a solid-state image pickup device disposed in the distal end portion of an insert part of an endoscope is covered with a flexible tube of a synthetic resin material in both a bendable portion and a flexible insert tube that constitutes the insert part.
In the bendable portion, however, the wall thickness of the flexible tube cannot be increased without restriction. Accordingly, the signal cable, which is merely covered with the flexible tube, must unavoidably be limp.
For this reason, it is likely that the signal cable will become curled in the bendable portion while the bendable portion is repeatedly bent with a small radius of curvature, and it will locally press other built-in components, e.g., a light guide fiber bundle for illumination, causing them to break down early.
In addition, if the signal cable is inferior in surface slip characteristics, it may damage other components incorporated in the flexible insert tube.
Under these circumstances, a prior art device, as shown for example in FIG. 7, has been arranged such that a signal cable is covered with thin, porous tetrafluoroethylene resin tape 91, which has superior slip properties and high flexibility, by winding the tape 91 double around the cable, and in the portion of the signal cable which is located in the bendable portion the tape 91 is tied tightly with thread 93, as shown in FIG. 8, thereby preventing the tape 91 from coming loose. In FIGS. 7 and 8, reference numeral 92 denotes signal wires, and 94 shielding wires which are provided around the signal wires 92.
However, since the porous tetrafluoroethylene resin tape 91 tears relatively easily, it is likely that the tape 91 will catch on a bending mechanism or other associated component and tear while the bendable portion is bent repeatedly, as shown in FIG. 9, causing the shielding and signal wires 94 and 92 to be exposed, resulting in electrical leakage.